A detection device and a corresponding detection method are described in German Patent Application No. DE 10 2004 006 015. In this case, a device is used to adjust a threshold value of a detection unit, preferably in an ultrasound system for vehicle surroundings detection. In addition to a transmission/reception device for transmitting a transmission burst at a predetermined pulse repetition rate and a predetermined signal frequency and for receiving a received signal, the device has a signal processing device for conditioning the received signal. In addition, the detection device is used to determine a received signal magnitude from the received signal as an interference level test after a first predetermined period of time starting from a signal burst within a predetermined second period of time. In order to adjust a threshold value of the detection device as a function of the detected received signal magnitude as an interference level test, the device also has a control unit. The same applies correspondingly to the method for adjusting a threshold value of the detection unit described in the above-mentioned patent application.
An object of the known device and the described method is to be able to use expanded detection functions even in dynamic surroundings in which an acoustic interference level may change rapidly, due, for example, to a passing two-cycle motorcycle, wind noise, and/or so-called microphonics. The microphonics depend on the engine load or the engine speed or even other vehicle vibrations.